1. Field of the Invention
The present invention relates to a body framework construction which is disposed at a lower part of a passenger compartment of a motor vehicle.
2. Description of the Related Art
As a framework construction of the related art which supports a lower part of a passenger compartment of a motor vehicle, there is a framework construction in which a front end portion of a floor panel which makes up a floor portion of the passenger compartment is joined to a dash panel disposed between an engine compartment and the passenger compartment and a rear end portion is joined to a rear seat cross member which extends in a transverse direction of the vehicle in the rear of a body. A tunnel portion where an exhaust pipe and a drive shaft pass are provided to pass through to the rear of the body is formed in a transversely central portion of a floor panel like the one described above. The tunnel portion has a U-shaped cross section and is configured to project upwards from the floor panel, and a backbone is mounted on an upper surface of the tunnel portion as a reinforcement member in such a manner as to extend in a longitudinal direction. The backbone is made, for example, of a plate-like member and is configured into a thin, long shape having a U-shaped cross section so as to extend along the tunnel portion in a matched fashion. A rear end portion of the backbone is disposed in front of the rear seat cross member, and the tunnel portion is disposed between the rear seat cross member and the backbone. (For example, refer to JP-A-2006-143178.)
In the vehicle body framework construction of the related art that has been described above, however, there have been the following problems inherent therein. Namely, since the floor panel is made up of the single plate member, it is easily subject to torsional deformation, and since the configuration is adopted in which the backbone intended to increase the strength is not directly joined to the rear seat cross member and is provided on only part of the floor panel, it has been difficult to secure high strength.